This application is related by subject matter to U.S. application Ser. No. 11/198,996, filed Aug. 8, 2005, entitled “Geo-Fencing in a Wireless Location System” (the entirety of which is hereby incorporated by reference), which is a continuation of U.S. application Ser. No. 11/150,414, filed Jun. 10, 2005, entitled “Advanced Triggers for Location Based Service Applications in a Wireless Location System,” which is a continuation-in-part of U.S. application Ser. No. 10/768,587, filed Jan. 29, 2004, entitled “Monitoring of Call Information in a Wireless Location System,” now pending, which is a continuation of U.S. application Ser. No. 09/909,221, filed Jul. 18, 2001, entitled “Monitoring of Call Information in a Wireless Location System,” now U.S. Pat. No. 6,782,264 B2, which is a continuation-in-part of U.S. application Ser. No. 09/539,352, filed Mar. 31, 2000, entitled “Centralized Database for a Wireless Location System,” now U.S. Pat. No. 6,317,604 B1, which is a continuation of U.S. application Ser. No. 09/227,764, filed Jan. 8, 1999, entitled “Calibration for Wireless Location System,” now U.S. Pat. No. 6,184,829 B1.
This application is also related by subject matter to Published U.S. Patent Application No. US20050206566A1, “Multiple Pass Location Processor,” filed on May 5, 2005, which is a continuation of U.S. application Ser. No. 10/915,786, filed Aug. 11, 2004, entitled “Multiple Pass Location Processor,” now U.S. Pat. No. 7,023,383, issued Apr. 4, 2006, which is a continuation of U.S. application Ser. No. 10/414,982, filed Apr. 15, 2003, entitled “Multiple Pass Location Processor,” now U.S. Pat. No. 6,873,290 B2, issued Mar. 29, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 10/106,081, filed Mar. 25, 2002, entitled “Multiple Pass Location Processing,” now U.S. Pat. No. 6,603,428 B2, issued Aug. 5, 2003, which is a continuation of U.S. patent application Ser. No. 10/005,068, filed on Dec. 5, 2001, entitled “Collision Recovery in a Wireless Location System,” now U.S. Pat. No. 6,563,460 B2, issued May 13, 2003, which is a divisional of U.S. patent application Ser. No. 09/648,404, filed on Aug. 24, 2000, entitled “Antenna Selection Method for a Wireless Location System,” now U.S. Pat. No. 6,400,320 B1, issued Jun. 4, 2002, which is a continuation of U.S. patent application Ser. No. 09/227,764, filed on Jan. 8, 1999, entitled “Calibration for Wireless Location System,” now U.S. Pat. No. 6,184,829 B1, issued Feb. 6, 2001.
A great deal of effort has been directed to the location of wireless devices, most notably in support of the Federal Communications Commission's (FCC) rules for Enhanced 911 (E911) Phase (The wireless Enhanced 911 (E911) rules seek to improve the effectiveness and reliability of wireless 911 service by providing 911 dispatchers with additional information on wireless 911 calls. The wireless E911 program is divided into two parts—Phase I and Phase II. Phase I requires carriers, upon valid request by a local Public Safety Answering Point (PSAP), to report the telephone number of a wireless 911 caller and the location of the antenna that received the call. Phase II requires wireless carriers to provide more precise location information, within 50 to 300 meters in most cases. The deployment of E911 has required the development of new technologies and upgrades to local 911 PSAPs, etc.) In E911 Phase II, the FCC's mandate included required location precision based on circular error probability. Network-based systems (wireless location systems where the radio signal is collected at the network receiver) were required to meet a precision of 67% of callers within 100 meters and 95% of callers within 300 meters. Handset-based systems (wireless location systems where the radio signal is collected at the mobile station) were required to meet a precision of 67% of callers within 50 meters and 95% of callers within 100 meters. Wireless carriers were allowed to adjust location accuracy over service areas so the accuracy of any given location estimation could not be guaranteed.
While some considerations, such as accuracy and yield (the number of successful locations per calls) were defined by the FCC for the single LBS service of E911, additional quality-of-service (QoS) parameters such as latency (time to location fix and delivery of the location estimate to the requesting or selected application) were not. The FCC concern with accuracy was for the particular instance of a cellular call being placed to an emergency services center (the 911 centers or PSAP). The state-of-the-art and the FCC's rigorous accuracy standards limited the technology choices for widely deployed location technologies. Network-based options for E911 Phase II included uplink-time-difference-of-arrival (U-TDOA), angle of arrival (AoA), and TDOA/AoA hybrids. Non-network-based location options for E911 Phase II included use of the Navistar Global Positioning System (GPS) augmented with data from a landside server that includes synchronization timing, orbital data (Ephemeris) and acquisition data (code phase and Doppler ranges).
Besides the FCC E911 compliant location systems for wireless voice communications, other wireless location systems using Time-of-Arrival (TOA), Time-Difference-of-Arrival (TDOA), Angle-of-Arrival (AoA), Power-of-Arrival (POA), Power-Difference-of-Arrival can be used to develop a location to meet specific location-based services (LBS) requirements.
In the Detailed Description section below, we provide further background on location techniques and wireless communications systems that may be employed in connection with the present invention. In the remainder of this Background section, we provide further background on wireless location systems.
Early work relating to Wireless Location Systems is described in U.S. Pat. No. 5,327,144, Jul. 5, 1994, “Cellular Telephone Location System,” which discloses a system for locating cellular telephones using time difference of arrival (TDOA) techniques. Further enhancements of the system disclosed in the '144 patent are disclosed in U.S. Pat. No. 5,608,410, Mar. 4, 1997, “System for Locating a Source of Bursty Transmissions.” Both of these patents are assigned to TruePosition, Inc., the assignee of the present invention. TruePosition has continued to develop significant enhancements to the original inventive concepts.
Over the past few years, the cellular industry has increased the number of air interface protocols available for use by wireless telephones, increased the number of frequency bands in which wireless or mobile telephones may operate, and expanded the number of terms that refer or relate to mobile telephones to include “personal communications services,” “wireless,” and others. The air interface protocols now used in the wireless industry include AMPS, N-AMPS, TDMA, CDMA, GSM, TACS, ESMR, GPRS, EDGE, UMTS WCDMA, and others.
The wireless communications industry has acknowledged the value and importance of the Wireless Location System. In June 1996, the Federal Communications Commission issued requirements for the wireless communications industry to deploy location systems for use in locating wireless 911 callers. Widespread deployment of these systems can reduce emergency response time, save lives, and save enormous costs because of reduced use of emergency response resources. In addition, surveys and studies have concluded that various wireless applications, such as location sensitive billing, fleet management, and others, will have great commercial value in the coming years.
As mentioned, the wireless communications industry uses numerous air interface protocols in different frequency bands, both in the U.S. and internationally. In general, neither the air interface nor the frequency bands impact the Wireless Location System's effectiveness at locating wireless telephones.
All air interface protocols use two categories of channels, where a channel is defined as one of multiple transmission paths within a single link between points in a wireless network. A channel may be defined by frequency, by bandwidth, by synchronized time slots, by encoding, shift keying, modulation scheme, or by any combination of these parameters. The first category, called control or access channel, is used to convey information about the wireless telephone or transmitter, for initiating or terminating calls, or for transferring bursty data. For example, some types of short messaging services transfer data over the control channel. Different air interfaces use different terminology to describe control channels but the function of the control channels in each air interface is similar. The second category of channel, known as voice or traffic channel, typically conveys voice or data communications over the air interface. Traffic channels come into use once a call has been set up using the control channels. Voice and user data channels typically use dedicated resources, i.e., the channel can be used only by a single mobile device, whereas control channels use shared resources, i.e., the channel can be accessed by multiple users. Voice channels generally do not carry identifying information about the wireless telephone or transmitter in the transmission. For some wireless location applications this distinction can make the use of control channels more cost effective than the use of voice channels, although for some applications location on the voice channel can be preferable.
The following paragraphs discuss some of the differences in the air interface protocols:
AMPS—This is the original air interface protocol used for cellular communications in the U.S. and described in TIA/EIA Standard IS 553A. The AMPS system assigns separate dedicated channels for use by control channels (RCC), which are defined according to frequency and bandwidth and are used for transmission from the BTS to the mobile phone A reverse voice channel (RVC), used for transmission from the mobile phone to the BTS, may occupy any channel that is not assigned to a control channel.
N-AMPS—This air interface is an expansion of the AMPS air interface protocol, and is defined in EIA/TIA standard IS-88. It uses substantially the same control channels as are used in AMPS but different voice channels with different bandwidth and modulation schemes.
TDMA—This interface, also known as D-AMPS and defined in EIA/TIA standard IS-136, is characterized by the use of both frequency and time separation. Digital Control Channels (DCCH) are transmitted in bursts in assigned timeslots that may occur anywhere in the frequency band. Digital Traffic Channels (DTC) may occupy the same frequency assignments as DCCH channels but not the same timeslot assignment in a given frequency assignment. In the cellular band, a carrier may use both the AMPS and TDMA protocols, as long as the frequency assignments for each protocol are kept separated.
CDMA—This air interface, defined by EIA/TIA standard IS-95A, is characterized by the use of both frequency and code separation. Because adjacent cell sites may use the same frequency sets, CDMA must operate under very careful power control, producing a situation known to those skilled in the art as the near-far problem, makes it difficult for most methods of wireless location to achieve an accurate location (but see U.S. Pat. No. 6,047,192, Apr. 4, 2000, Robust, Efficient, Localization System, for a solution to this problem). Control channels (known in CDMA as Access Channels) and Traffic Channels may share the same frequency band but are separated by code.
GSM—This air interface, defined by the international standard Global System for Mobile Communications, is characterized by the use of both frequency and time separation. GSM distinguishes between physical channels (the timeslot) and logical channels (the information carried by the physical channels). Several recurring timeslots on a carrier constitute a physical channel, which are used by different logical channels to transfer information—both user data and signaling.
Control channels (CCH), which include broadcast control channels (BCCH), Common Control Channels (CCCH), and Dedicated Control Channels (DCCH), are transmitted in bursts in assigned timeslots for use by CCH. CCH may be assigned anywhere in the frequency band. Traffic Channels (TCH) and CCH may occupy the same frequency assignments but not the same timeslot assignment in a given frequency assignment. CCH and TCH use the same modulation scheme, known as GMSK. The GSM General Packet Radio Service (GPRS) and Enhanced Data rates for GSM Evolution (EDGE) systems reuse the GSM channel structure, but can use multiple modulation schemes and data compression to provide higher data throughput. GSM, GPRS, and EDGE radio protocols are subsumed by the category known as GERAN or GSM Edge Radio Access Network.
UMTS—Properly known as UTRAN (UMTS Terrestrial Radio Access Network), is an air interface defined by the international standard third Generation Partnership program as a successor to the GERAN protocols. UMTS is also sometimes known as WCDMA (or W-CDMA), which stands for Wideband Code Division Multiple Access. WCDMA is direct spread technology, which means that it will spread its transmissions over a wide, 5 MHz carrier.
The WCDMA FDD (Frequency Division Duplexed) UMTS air interface (the U-interface) separates physical channels by both frequency and code. The WCDMA TDD (Time Division Duplexed) UMTS air interface separates physical channels by the use of frequency, time, and code. All variants of the UMTS radio interface contain logical channels that are mapped to transport channels, which are again mapped to W-CDMA FDD or TDD physical channels. Because adjacent cell sites may use the same frequency sets, WCDMA also uses very careful power control to counter the near-far problem common to all CDMA systems. Control channels in UMTS are known as Access Channels whereas data or voice channels are known as Traffic Channels. Access and Traffic Channels may share the same frequency band and modulation scheme but are separated by code. Within this specification, a general reference to control and access channels, or voice and data channels, shall refer to all types of control or voice and data channels, whatever the preferred terminology for a particular air interface. Moreover, given the many types of air interfaces (e.g., IS-95 CDMA, CDMA 2000, UMTS, and W-CDMA) used throughout the world, this specification does not exclude any air interface from the inventive concepts described herein. Those skilled in the art will recognize other interfaces used elsewhere are derivatives of or similar in class to those described above.
GSM networks present a number of potential problems to existing Wireless Location Systems. First, wireless devices connected to a GSM/GPRS/UMTS network rarely transmit when the traffic channels are in use. The use of encryption on the traffic channel and the use of temporary nicknames (Temporary Mobile Station Identifiers (TMSI)) for security render radio network monitors of limited usefulness for triggering or tasking wireless location systems. Wireless devices connected to such a GSM/GPRS/UMTS radio network merely periodically “listen” for a transmission to the wireless device and do not transmit signals to regional receivers except during call setup, voice/data operation, and call breakdown. This reduces the probability of detecting a wireless device connected to a GSM network. It may be possible to overcome this limitation by actively “pinging” all wireless devices in a region. However, this method places large stresses on the capacity of the wireless network. In addition, active pinging of wireless devices may alert mobile device users to the use of the location system, which can reduce the effectiveness or increase the annoyance of a polling location-based application.
The above-cited application Ser. No. 11/198,996, “Geo-Fencing in a Wireless Location System,” describes methods and systems employed by a wireless location system to locate a wireless device operating in a defined geographic area served by a wireless communications system. In such a system, a geo-fenced area may be defined, and then a set of predefined signaling links of the wireless communications system may be monitored. The monitoring may also include detecting that a mobile device has performed any of the following acts with respect to the geo-fenced area: (1) entered the geo-fenced area, (2) exited the geo-fenced area, and (3) come within a predefined degree of proximity near the geo-fenced area. In addition, the method may also include, in response to detecting that the mobile device has performed at least one of these acts, triggering a high-accuracy location function for determining the geographic location of the mobile device. The present application describes methods and systems for using the concept of a geo-fenced area to enable, selectively enable, limit, deny, or delay certain functions or services based on the calculated geographic location and a pre-set location area defined by local, regional, or national legal jurisdictions. The present invention, however, is by no means limited to systems employing the geo-fencing technologies described in the above-cited application Ser. No. 11/198,996.